Comparison of Absorption and Adsorption Processes for CO2 Dehydration

Abstract

Captured carbon dioxide (CO2) must be dehydrated prior to transport or storage because of possibilities for corrosion and hydrate formation. CO2 dehydration can be performed by absorption, typically into triethylene glycol (TEG) followed by desorption or by adsorption on a solid (typically a molecular sieve) followed by desorption. In this work, the process simulation program Aspen HYSYS is used to calculate material and heat balances for a TEG based absorption process and a molecular sieve adsorption process to achieve less than 30 ppm water in the dehydrated gas. The absorption and stripping columns were modelled using a specified Murphree stage efficiency on each absorption and stripping stage. In the base case, the absorption and adsorption pressure was 40 bar and the inlet temperature was 30 °C. An additional stripping column was added below the desorption column to obtain a low water content. In the molecular sieve based process, all the process units except the adsorption/stripping units were simulated in Aspen HYSYS. It is simulated reasonable process alternatives for CO2 dehydration down to water levels of 30 and 5 ppm. The simulations combined with cost estimation indicate that a TEG based process is the most economic process both for dehydration down to 30 ppm and to 5 ppm water in dehydrated gas.